1. Field of the Invention
The present invention relates to the field of life-saving in swimming-pools or in the sea and to the surveillance of beaches.
2. Description of the Prior Art
For sea rescue work, equipment for the prevention of drowning accidents as employed in accordance with conventional practice essentially consists of a VHF radio transmitter set. When a person equipped with a radio transmitter of this type falls into the sea, the transmitter is turned-on by a means for closing a contact by conduction of water and transmits a VHF signal which triggers the alarm or emergency aid means. However, this system is unreliable since it operates only when the person is not totally submerged.
The problem to be solved in a swimming-pool and for the surveillance of beaches is to be able to make a distinction between a normal bather (even if he or she remains underwater for a fairly long time) and a submerged person who is in danger of drowning. Since radio waves propagate only very weakly underwater, the use of a radio transmitter alone is not sufficient for life-saving in a swimming-pool or in the vicinity of beaches.